Mapping oil spills in California

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# read in spatial data
counties <- read_sf(here("_posts", "2021-03-14-map", "ca_counties", layer = "CA_Counties_TIGER2016.shp")) %>% 
  clean_names()

oil_spills <- read_sf(here("_posts", "2021-03-14-map","Oil_Spill_Incidents", layer = "Oil_Spill_Incident_Tracking_%5Bds394%5D.shp")) %>% 
  clean_names()

# check crs
# st_crs(counties) # WGS 84
# st_crs(oil_spills) # WGS 84

Oil spill locations

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# set to interactive viewing mode
tmap_mode("view")

# make exploratory map
tm_shape(counties)+
  tm_borders("black")+
  tm_shape(oil_spills)+
  tm_dots("red")

Figure 1. California oil spills (2008). Oil spills that occured in California in 2008 are shown (red points, n = 3,237). Data source: CA DFW Oil Spill Incident Tracking

Oil spills by county

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# spatial join counties with spills and summarize number of spills per county
county_spills <- st_join(counties, oil_spills) %>% 
  group_by(name) %>% 
  summarize(spill_count = count_if("Inland", inlandmari))

# make static chloropleth map of  
ggplot()+
  geom_sf(county_spills, mapping = aes(fill = spill_count))+
  theme_void()+
  scale_fill_steps(low = "white",
                    high = "#033296",
                    n.breaks = 6,
                    name = "Number of inland\noil spills")+
  theme(legend.position = c(0.85, 0.75))

Figure 2. Oil spills by county (2008). The number of inland oil spills that occurred in each county in California in 2008 is indicated by color, with darker colors indicating more spills. Data source: CA DFW Oil Spill Incident Tracking